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Year 3 Skills > ECG made easy - 2&3 > Flashcards

ECG made easy - 2&3 Flashcards

1
Q

(ECG made easy: chapter 2) In what order does the wave of depolarisation normally spread?

A

SA –> AV –> bundle of His –> right/ left bundle branches –> Purkinje fibres

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2
Q

Which leads usually form the rhythm strips and why?

A

lead II or V1 because the P wave is most clearly seen on these leads

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3
Q

What does a prolonged PR interval suggest ?

A

First degree heart block

First degree heart block is not in itself important, but it may be a sign of coronary artery disease, acute rheumatic carditis, digoxin toxicityor electrolyte disturbances.

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4
Q

How long is a PR interval usually?

A

220ms

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5
Q

Describe second degree heart block.

A

When excitation fails to pass through the AV node of the bundle of His

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6
Q

What are the three variations of 2DHB?

A
  1. Progressive lengthening of PR interval then failure of conduction of an atrial beat - Wenckeback/Mobitz type I
  2. Constant PR interval but occasionally there is depolarisation without a subsequent ventricular depolarisation - Mobitz type 2 phenomenon
  3. Alternate conducted and nonconducted atrial beats (or 1 conducted and 3 nonconducted i.e. 3:1) Noof P waves to QRS complexes.
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7
Q

What is the difference between Mobitz type 1 and type 2?

A
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8
Q

What is the diagnosis?

A
  • Second degree heart block (2:1)
  • Two P waves to every QRS complex
  • Normal and constant, PR interval in the conducted beats
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9
Q

What is the diagnosis?

A

Second degree heart block (2:1 type)

P wave in the T wave can be identified because of its regularity

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10
Q

What is the diagnosis?

A

Third degree heart block - P wave rate 90/min

No relationship between P waves and QRS complex (QRS rate is 36/min)

Abnormally shaped QRS complexes, because of abnormal spread of depolarisation from a ventricular focus.

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11
Q

Describe why this is a complete (3o) heart block.

A
  • Sinus rhythm but no P waves are conducted
  • Right axis deviation
  • Broad QRS complexes (duration 160ms)
  • RBBB pattern
  • In most patients this is caused by fibrosis of the bundle of His
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12
Q

Which is more problematic: RBBB or LBBB?

A

RBBB patterns with a normal QRS complex duration are normal in helathy people.

LBBB is always an indication of heart disease, usually of the left ventricle. Left ventricle also exerts more influence on the ECG than does the right ventricle.

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13
Q

What are the right and left ventricular leads?

A

Right ventricular lead (V1)

Left ventricular lead (V6)

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14
Q

Describe the pattern seen in a RBBB.

A
  1. no depolarisation occurs down the RBB but septum is depolarised from the left as usual causing an R wave in V1 and small Q wave in V6
  2. Excitation spreads in left ventricle –> S wave in V1 and R wave in V6
  3. It takes longer for depolarisation to reach the right ventricle so this causes a second R wave in V1 and a wide and deep S wave and wide QRS complex in V6

RSR1 pattern with a normal width is called partial RBBB and is usually a normal variant.

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15
Q

Describe the pattern seen in a LBBB.

A
  1. Conduction down LBB fails so conduction occurs right to left –> causing a small Q wave in lead V1 and an R wave in lead V6
  2. Right venricle (smaller mass) depolarisation causes an R wave in V1 and an S wave (small notch) in V6.
  3. Left ventricle is then depolarised causing an S wave in V1 and another R wave in V6
  4. LBBB is associated with T wave inversion in lateral leavds (I, VL, V5, V6)

NB: any upward deflection no matter how small is an R wave and any downward deflection, however small, following an r wave is an S wave.

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16
Q

How do you distinguish a LBBB from a RBBB?

A
  • RBBB is best seen in lead V1, where there is an RSR1 pattern
  • LBBB is seen in lead V, where there is a broad QRS complex with a notched top, which resembles the letter “M” and is there known as an “M” pattern. The complete picture witha W pattern in lead V1, is often not fully developed.
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17
Q

What is the diagnosis?

A

Sinus rhythm with RBBB

  • Sinus rhythm, rate 60/min
  • Normal PR interval
  • Normal cardiac axis
  • Wide QRS complexes (160ms)
  • RSR1 pattern in lead V1 and deep, wide S in lead V6
  • Normal ST segments and T waves
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18
Q

What is the diagnosis?

A

Sinus rhythm with left bundle branch block

  • Sinus rhythm, rate 100/min
  • Normal PR interval
  • Normal cardiac axis
  • Wide QRS complexes (160ms)
  • M pattern in the QRS complexes, best seen in leads I, VL, V5, V6
  • Inverted T waves in leads I, II, VL
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19
Q

Describe the divisions of the bundle of His.

A
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20
Q

Which ventricle has more of an influence of the cardiac axis?

A

The left ventricle (depolarised through the posterior fascicle) contains more muscle than the right, it has more influence on the cardiac axis.

If the anterior fascicle fails to conduct the, the left ventricle has to be depolarised through the posterioir fascicle and so the cardiac axis rotates upwards.

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21
Q

What is a left anterior hemiblock caused by?

A

Left anterior fascicular block which can cause left axis deviation

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22
Q

What does the ECG show?

A
  • Sinus rhythm with left axis deviation (otherwise normal)
  • Sinus rhythm, rate 80/min
  • Left axis deviation, QRS complex upright in lead I, but downward (dominant S wave) in lead II and III
  • Normal QRS complexes, ST segments and T waves
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23
Q

What is a bifascicular block and how does it present?

A

When the right bundle branch and left anterior fascicle are blocked the ECG shows RBBB and left axis deviation (widespread damage to the conducting system)

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24
Q

What does this ECG show?

A

Bifascicular block

  • Sinus rhythm rate 90/min
  • Left axis deviation (dominant S wave in leads II and III)
  • Right BBB (RSR1 pattern in lead V1 and deep wide S wave in lead V6)
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25
Q

List and summarise the different conduction problems that can occur in the heart. Which ones require treatment?

A
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26
Q

What is an easy way of distinguishing RBBB and LBBB?

A

RBBB has an RSR1 pattern in lead V1

LBBB has a letter M pattern in lead V6

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27
Q

What is a sinus rhythm?

A

Depolarisation that begins in the SA node is said to be in sinus rhythm

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28
Q

What is an arrhythmia?

A

When depolarisation of the heart begins somewhere other than the SA node. Arrhythmias should be identified from the lead in which the P waves can be seen most easily.

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29
Q

What is the rate of discharge of the SA node influenced by?

A

Vagus nerve

Reflexes originating in the lungs

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30
Q

What do you call changes in heart rate associated with respiration?

A

Sinus arrhythmia - often seen in young people

31
Q

List the causes of sinus bradycardia and sinus tachycardia.

A

Sinus bradycardia:

  • athletic training
  • fainting attacks
  • hypothermia
  • myxoedema
  • also seen after MI

Sinus tachycardia:

  • exercise
  • fear
  • pain
  • haemorrhage
  • thyrotoxicosis
32
Q

Where can abnormal cardiac rhythms originate?

A
  1. Atrial muscle
  2. Region around the AV node - “nodal”/”junctional”
  3. Ventricular muscle
33
Q

Will a supraventricular rhythm look abnormal?

A

No - because depolarisation still spreads to the ventricles in the same way so QRS is normal whether depolarisation was initiated by SA/atrial muscle/junctional region

34
Q

Describe the appearance of a ventricular rhythm on an ECG.

A

Depolarisation spreads through ventricles by slower Purkinje fibres so the QRS complex will be wide and abnormally shaped and repolarisation (T wave) will also be abnormal

35
Q

Ventricular rhythms have wide QRS complexes and supraventricular have narrow QRS complexes. What is the exception to this rule?

A

A supraventricular rhythm with a R/LBBB

Wolff-Parkinson-White (WPW) syndrome

36
Q

What are the 4 ways of categorising abnormal rhythms arising in the atrial muscle/junctional region/ventricular muscle?

A

Bradycardias - slow and sustained

Tachycardias - fast and sustained

Extrasystoles - early single beats

Fibrillation - activation of atria or ventricles is totally disorganised

37
Q

Why do random areas of the heart not sponatneously depolarise?

A

Secondary sides have a lower intrinsic frequency of depolarisation than the SA node.

38
Q

What is the rate of depolarisation of the SA node? If it failed to depolarise what would the HR be?

A

SA node gives a normal heart rate of about 70/min

Atrial muscle/junctional region would give a rate of 50/min

Ventricular focus (if His is blocked) would give a rate of 30/min

These are called ESCAPE RHYTHMS(atrial escape/nodal escape/ventricular escape). Commonly seen in acute phases of a heart attack. These are the BRADYCARDIAS.

39
Q

What is an accelerated idioventricular rhythm?

A

Rhythm of heart can sometimes be controlled by a ventricular escape.This gives a frequency of discharge faster than that seen in a complete heart block. This is usually benign and should not be treated but is sometimes seen in acute MI.

40
Q

Compare the patterns seen in atrial vs junctional escape.

A

Atrial - SA fails after beat, abnormal P wave after delay followed by normal QRS.

Nodal - sinus rhythm and junctional escpae rhythm have different rates, no P waves in junctional beats and normal QRS.

41
Q

Compare complete heart block vs ventricular escape.

A

Complete heart block - normal p waves, but QRS abnormal, P and QRS have different rates.

Ventricular escape - after a number of sinus beats SA fails, pause, single wide QRS, ventricular focus for one beat then sinus rhythm restored.

42
Q

What is the difference between extrasystole and an escape beat?

A

Escape beat - comes later after sinoatrial node fails to initiate depolarisation and another focus takes over to initiate a beat.

Extrasystole - same as an escape beat but comes early

43
Q

What type of extrasystole is shown here?

A

Atrial extrasystoles have abnormal P waves

Junctional extrasystoles have no P waves at all or the P wave appear immediately before or immediately after the QRS complex.

44
Q

How do ventricular extrasystoles appear on an ECG?

A
  • Abnormal QRS complexes which can be wide and of any shape
  • Usually of no importance but if they occur early they can induce ventricular fibrillation –> dangerous
45
Q

What are the effects of supraventricular and ventricular extrasystoles on the followinng P wave?

A
  • Supraventricular - resets the P wave cycle
  • Ventricular - does not affect the SA node so the next P ave appears at the predicted time
46
Q

List 3 types of supraventricular tachycardia.

A
  • Atrial tachycardia (abnormal focus in the atrium)
  • Atrial flutter (with e.g. 2:1 block or with carotid sinus pressure)
  • Junctional tachycardia
47
Q

What type of tachycardia is this?

A

Atrial tachycardia - atria depolarise faster than 150/min.

48
Q

What happens when in atrial tachycardia the rate becomes >200/min?

A

If it becomes faster than 200/min then atrioventricular block occurs because the AV node cannot conduct atrial rates of discharge faster than 200/min. some P waves may not be followed by QRS complexes.

The difference between this and 2o heart block is that here the AV node and His bundle are still conducting normally.

49
Q

What is atrial flutter?

A

An atrial rate >250/min with no flat baseline between P waves.

50
Q

What type of tachycardia is shown in this ECG?

A

A narrow complex tachycardia with a ventricular rate of about 125-150/min should always alert you to the possibility of atrial flutter with 2:2 block. Look at the lead where P waves are most easily seen. (look at II, VR, VF)

51
Q

What is seen on this ECG?

A
  • Atrial flutter with 2:1 block
  • P waves at 300/min
  • Regular QRS with rate 160/min
  • Narrow QRS complexes with normal shape
  • Normal T waves (best seen in the V leads - in limb leads it is difficult to distinguish between T and P waves)
52
Q

What type of tachycardia is seen on this ECG?

A

Junctional tachycardia - AV node is depolarising frequently so P wave is very close to QRS or not seen at all. QRS is usually a normal shape because the ventricles continue to be activated through His bundle.

Seen above:

  • No P waves
  • Regular QRS with rate 200/min
  • Narrow QRS with normal shape
  • Normal T waves
53
Q

What is the benefit of carotid sinus pressure? What is its effect on ventricular arrhythmias?

A
  • It may make the nature of supraventricular tachycardias more obvious.
  • Carotid sinus pressure activates a reflex that leads to vagal stimulation of the SA and AV nodes. This causes a reduction in discharge of SA node and an increase in delay of conduction in the AV node.
  • The latter may be therapeutic/diagnostic
  • Carotid sinus pressure abolishes some supraventricular arrhythmias and slows the ventricular rate in others BUT it has no effect on ventricular arrhythmias.
54
Q

What does ventricular tachycardia look like on an ECG?

A

Wide and abnormal QRS complexes (also seen in BBB)

55
Q

What is shown here?

A

Ventricular tachycardia

  • No P waves
  • Regular QRS complexes, rate 200/min
  • Broad QRS complexes, duration 280ms, with a very abnormal shape
  • No identifiable T waves
56
Q

What is the rhythm of this ECG? Which type of block is shown here?

A

WiLLiam (V1) MaRRow(V6)

Sinus rhythm with left bundle branch block

  • Each QRS is preceded by P with constant PR interval so sinus rhythm
  • QRS complexes are wide and the T waves are inverted
  • This trace comes from V6 and the M pattern and inverted T wave are characteristic of LBBB
57
Q

How would you distinguish between a ventriculr and supraventricular tachycardia with bundle branch block?

A
  1. P waves - look how they relate to QRS
  2. QRS complex - compare the normal QRS to the WRS during tachycardia. If the patient has BBB when in sinus rhythm then the QRS complex will have same shape during tachycardia.
  3. QRS width - more than 4 small squares (160ms) = rhythm is ventricular in origin
  4. Left axis deviation during tachycardia indicates ventricular origin, as does any change in axis compared to sinus
  5. Very irregular QRS in tachycardia probably means atrial fibrillation with BBB
58
Q

What is fibrillation? How does atrial fibrillation appear on an ECG?

A

The asynchronous contraction of muscle fibres of the atria or ventricles

Atrial fibrillation - no P waves on the ECG. Only an irregular line although there may be some flutter-like wave for 2-3s.

59
Q

Why are there no P waves on an ECG showing atrial fibrillation?

A

The AV node is constantly being bombarded with depolarisation waves of varying strength. BUT QRS shape is still normal because AV conducts at an “all or nothing fashion” so depolarisation waves passing down the bundle via normal route. However they are irregular.

60
Q

What type of tachycardia is shown here?

A

Atrial fibrillation - no P waves, irregular QRS complexes, normally shaped QRS complexes, in V1 there is some resemblance to arial flutter which is commonly seen in atrial fib.

61
Q

What is the diagnosis?

A

Atrial fibrillation - no P waves, irregular baseline, irregular QRS complexes with a rate varying between 75/min and 190/min, narrow QRS complexes of normal shape, depressed ST segments in leads V5-V6 (digoxin effect), normal T waves.

62
Q

What is shown here?

A

Ventricular fibrillation - no QRS complexes can be identified and the ECG is totally disorganised. By this time the patient will usually have lost consciousness.

63
Q

What is Wolff-Parkinson-White (WPW) syndrome?

A
  • Occurs when people have an extra or “accessory” conducting bundle other than His that is connecting the atria and ventricles.
  • This is usually on the left side of the heart and this bundle has no AV node to delay conduction.
  • The wave of excitation therefore reaches the ventricle early and “pre-excitation” occurs.
  • The QRS shows an early slurred upstroke called a “delta wave”. The second part of the QRS is normal as conduction through the His bundle usually catches up with the pre-excitation.
64
Q

What is the diagnosis and why?

A

Wolff-Parkinson-White syndrome

  • Sinus rhythm rate 125/min
  • Right axis deviation
  • Short PR interval
  • Slurred upstroke of the QRS complex, best seen in leads V3 and V4. Wide QRS complex due to this “delta” wave
  • Dominant R wave in lead V1
65
Q

What can be the result of a sustained Wolff-Parkinson-White Syndrome?

A
  • It can cause paroxysmal tachycardia which means that depolarisation can spread down the His bundle an back up the accessory pathway to reactivate the atrium.
  • This “re-entry” circuit –> sustained tachycardia
66
Q

What is the origin of most “junctional” achycardias?

A

Usually junctional tachycardias are due to re-entry circuits around the AV node so are properly called AVNRTs (atrioventricular nodal re-entry tachycardias”

67
Q

How would you treat a patient with bradycarda that is affecting circulation?

A

Atrpine

If this is ineffective, then a pacemaker may be required temporarily or permanently.

68
Q

What is the first treatment of any abnormal tachycardia?

A

Carotid sinus pressure

69
Q

What is the effect of carotid sinus pressure on….

  • Sinus tachycardia
  • Atrial and junctional tachycardia
  • Atrial flutter
  • Atrial fibrillation and ventricular tachycardia
A
  • Sinus tachycardia - temporary slowing of HR
  • Atrial and junctional tachycardia - may terminate the arrhythmia or have no effect
  • Atrial flutter - temporary increase in block e.g. 2:1 to 3:1
  • Atrial fibrillation and ventricular tachycardia - no effect
70
Q

How can you tell that this is a pacemaker trace?

A
  • Occasional P waves are visible - but not related to the QRS complexes
  • QRS complexes are preceded by a brief spike, representing the pacemaker stimulus
  • QRS complexes are broad, because pacemakers stimulate the right ventricle and cause “ventricular” beats
71
Q

True or false?

All supraventricular rhythms have wide QRS complexes.

A

False - all supraventricular rhythms have normal QRS complexes provided there is no bundle branch block or WPW syndrome(pre-excitation).

Ventricular rhythms cause wide and abnormal QRS complexes and abnormal T waves.

72
Q

True or false?

Apart from the rate, the ECG patterns of an escape rhythm, an extrasystole and atachycardia arising in any one part of theheart are the same.

A

True

73
Q

Identification of rhythm abnormalities:

  1. Is the abnormality occasional or sustained?
  2. Are there any P waves?
  3. Are there as many QRS complexes as P waves?
  4. Are the ventricles contracting regularly or irregularly?
  5. Is the QRS complex of normal shape?
  6. What is the ventricular rate?
A

Year 3 Skills (3 decks)

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